Elliptic Flow and Semi-hard Scattering at SPS

Results on elliptic flow and two-particle correlations in the semi-hard regime are presented.Comment: 4 pages, 4 figures, 3 of which contain 2 eps file

Elliptic flow contribution to two-particle correlations at different orientations to the reaction plane

Collective anisotropic particle flow, a general phenomenon present in relativistic heavy-ion collisions, can be separated from direct particle-particle correlations of different physics origin by virtue of its specific azimuthal pattern. We provide expressions for flow-induced two-particle azimuthal correlations, if one of the particles is detected under fixed directions with respect to the reaction plane. We consider an ideal case when the reaction plane angle is exactly known, as well as present the general expressions in case of finite event-plane resolution. We foresee applications for the study of generic two-particle correlations at large transverse momentum originating from jet fragmentation.Comment: 5 pages, 3 figures, to be published as Rapid Communications in Phys.Rev.C Re-submit paper to with small improvements in text for better understanding, some minor changes in notation, and correcting one formula where a summation was forgotten. One new reference, one reference to conference report removed since full paper was already reference

Breakup of Shearless Meanders and "Outer" Tori in the Standard Nontwist Map

The breakup of shearless invariant tori with winding number $\omega=[0,1,11,1,1,...]$ (in continued fraction representation) of the standard nontwist map is studied numerically using Greene's residue criterion. Tori of this winding number can assume the shape of meanders (folded-over invariant tori which are not graphs over the x-axis in $(x,y)$ phase space), whose breakup is the first point of focus here. Secondly, multiple shearless orbits of this winding number can exist, leading to a new type of breakup scenario. Results are discussed within the framework of the renormalization group for area-preserving maps. Regularity of the critical tori is also investigated.Comment: submitted to Chao

Crossing barriers in planetesimal formation: The growth of mm-dust aggregates with large constituent grains

Collisions of mm-size dust aggregates play a crucial role in the early phases of planet formation. We developed a laboratory setup to observe collisions of dust aggregates levitating at mbar pressures and elevated temperatures of 800 K. We report on collisions between basalt dust aggregates of from 0.3 to 5 mm in size at velocities between 0.1 and 15 cm/s. Individual grains are smaller than 25 \mum in size. We find that for all impact energies in the studied range sticking occurs at a probability of 32.1 \pm 2.5% on average. In general, the sticking probability decreases with increasing impact parameter. The sticking probability increases with energy density (impact energy per contact area). We also observe collisions of aggregates that were formed by a previous sticking of two larger aggregates. Partners of these aggregates can be detached by a second collision with a probability of on average 19.8 \pm 4.0%. The measured accretion efficiencies are remarkably high compared to other experimental results. We attribute this to the rel. large dust grains used in our experiments, which make aggregates more susceptible to restructuring and energy dissipation. Collisional hardening by compaction might not occur as the aggregates are already very compact with only 54 \pm 1% porosity. The disassembly of previously grown aggregates in collisions might stall further aggregate growth. However, owing to the levitation technique and the limited data statistics, no conclusive statement about this aspect can yet be given. We find that the detachment efficiency decreases with increasing velocities and accretion dominates in the higher velocity range. For high accretion efficiencies, our experiments suggest that continued growth in the mm-range with larger constituent grains would be a viable way to produce larger aggregates, which might in turn form the seeds to proceed to growing planetesimals.Comment: 9 pages, 20 figure

The outcome of protoplanetary dust growth: pebbles, boulders, or planetesimals? I. Mapping the zoo of laboratory collision experiments

The growth processes from protoplanetary dust to planetesimals are not fully understood. Laboratory experiments and theoretical models have shown that collisions among the dust aggregates can lead to sticking, bouncing, and fragmentation. However, no systematic study on the collisional outcome of protoplanetary dust has been performed so far so that a physical model of the dust evolution in protoplanetary disks is still missing. We intend to map the parameter space for the collisional interaction of arbitrarily porous dust aggregates. This parameter space encompasses the dust-aggregate masses, their porosities and the collision velocity. With such a complete mapping of the collisional outcomes of protoplanetary dust aggregates, it will be possible to follow the collisional evolution of dust in a protoplanetary disk environment. We use literature data, perform own laboratory experiments, and apply simple physical models to get a complete picture of the collisional interaction of protoplanetary dust aggregates. In our study, we found four different types of sticking, two types of bouncing, and three types of fragmentation as possible outcomes in collisions among protoplanetary dust aggregates. We distinguish between eight combinations of porosity and mass ratio. For each of these cases, we present a complete collision model for dust-aggregate masses between 10^-12 and 10^2 g and collision velocities in the range 10^-4 to 10^4 cm/s for arbitrary porosities. This model comprises the collisional outcome, the mass(es) of the resulting aggregate(s) and their porosities. We present the first complete collision model for protoplanetary dust. This collision model can be used for the determination of the dust-growth rate in protoplanetary disks.Comment: accepted by Astronomy and Astrophysic

Fourier Transforms of Lorentz Invariant Functions

Fourier transforms of Lorentz invariant functions in Minkowski space, with support on both the timelike and the spacelike domains are performed by means of direct integration. The cases of 1+1 and 1+2 dimensions are worked out in detail, and the results for 1+n dimensions are given.Comment: 15 pages, 1 figur

11th–12th Grade: English Level 2, Learning Packet #3 • Theme: Susan B. Anthony

Day 1 • Journal: in your opinion, why is it important to vote?, Who was Susan B. Anthony?, Science: climate and biome where you\u27re from Day 2 • Journal: what are some things you are good at?, Past and present tense, Past and present tense: play, Science: weather near the equator, Biomes Day 3 • Journal: what was your favorite day of school?, Picture analysis, Science: climate far from the equator, Forests, Draw a picture Day 4 • Journal: what is a time you convinced someone to do something?, The 19th Amendment, Science: clothes near the equator, Grasslands, Deserts Day 5 • Journal: what are some things you want everyone to know about you?, Who should vote?, Do you think 16-year olds should vote?, Science: clothes far from the equator, Tundra References My Packet Journal Reference Shee

Dependence of lepton pair emission on EoS and initial state

We present results from a hydrodynamic calculation for thermal emission of lepton pairs in central lead-lead collisions at the CERN SPS energy. Dependence of the emission on the initial conditions and Equation of State (EoS) is considered and the spectra are compared with CERES data and calculated distribution of Drell--Yan pairs.Comment: 4 pages, includes 4 ps-figures, talk at Quark Matter'97, Tsukuba, Japa

11th–12th Grade: English Level 2, Learning Packet #1 • Theme: U. S. Bill of Rights

Day 1 • What is the Constitution?, Your rights in the United States, Science: water cycle Day 2 • Your rights in the United States: journal, What is the Bill of Rights?, Bill of Rights chart, Condensation and precipitation Day 3 • Your rights in the United States: protest, Using your vocabulary, Opinion writing, Clouds Day 4 • Your rights in the United States: journal, Vocabulary review, States of water Day 5 • Your rights in the United States: draw a picture, How does your picture show equality?, Solids, liquids, and gas examples My Packet Journal Reference Sheet Answer Key